Many turbine engines have fans formed by a plurality of blades. One example fan blade includes an aluminum substrate or fan blade body. A polyurethane coating is applied over the fan blade body. In order to obtain better fan performance, an outer air seal is provided in the form of an abradable rub strip. During operation of the gas turbine engine, a tip of the fan blade may rub against the adjacent outer air seal rub strip. During the rub event, the tip may wear and heat may be generated. To this end, the tip of the fan blade body has been anodized to create a hard coating layer.
Heat is generated when the blade hard coating rubs against the abradable rub strip. Because of the very low thermal conductivity (˜0.1 W/m K) of a typical abradable rub strip material as compared to the hard coating layer conductivity of ˜30 W/m K and the aluminum fan body conductivity of ˜160 W/m K, most of the heat generated during a rub event is conducted into the fan blade. Such conduction can cause the blade temperature near the tip to exceed the capability of the polyurethane, and results in degradation of the bonding of polyurethane to the aluminum blade.